Why the study?
Pulmonary arterial hypertension reduces perfused functional capillary surface area, leading to the hypothesis that exercising patients with pulmonary arterial hypertension cannot recruit functional capillary surface area normally.
Does exercise induce pulmonary capillary recruitment in patients with severe pulmonary arterial hypertension?
Does exercise induce pulmonary capillary recruitment in patients with severe pulmonary arterial hypertension?
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This study provides the first direct measurements showing that patients with severe PAH fail to recruit functional capillary surface area during exercise.
The human lung normally accommodates exercise-induced cardiac output increases mainly via recruitment of non-concomitantly perfused pulmonary capillaries. Recruitment is detectable by measuring the first-pass transpulmonary metabolism of 3 H-benzoyl-Phe-Ala-Pro, providing an estimate of functional capillary surface area (FCSA). Pulmonary arterial hypertension (PAH) results from luminal narrowing of small precapillary arterioles, reducing downstream perfused FCSA. We hypothesized that exercising PAH patients would not be able to recruit FCSA normally. We studied two patients with severe PAH. Despite exercising to maximal dyspnea, neither could recruit FCSA. These limited data are the first direct measurements of FCSA in exercising PAH patients.
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Langleben et al. (2026) studied this question.
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